1. Field of the Invention
The invention is directed to a method and apparatus for storing and rotating bit patterns. The bit patterns can be written into and in turn read out from matrix cells of a memory matrix. A bit pattern represents image information resolved into its individual pixels. Such image information that has been are processed, for example, in picture screen devices and other display units and in copier and printer devices for reproducing the image information on a recording medium.
2. Description of the Related Art
U.S. Pat. No. 5,012,434 discloses an electrographic printer that receives image information to be printed from a data processing device. This encoded image information is converted into a bit pattern by a printer controller and potentially rotated. The bit pattern is read out to a following reproduction means that transfers the bit pattern and, thus, the image information onto a recording medium.
Memory matrices are usually employed for rotating the bit patterns, the matrix cells of the memory matrices being capable of being randomly accessed with the assistance of peripheral selection elements. For example, it is thus possible to write or read entire rows or entire columns into and out of the memory matrix in parallel. To that end, each matrix cell comprises exactly one memory cell in which one pixel can be deposited in the form of a logical zero or one. Each matrix cell is respectively connected via a first line to a row multiplexer and via a second line to a column multiplexer. The column multiplexers and row multiplexers thereby serve as peripheral selection elements. Dependent on the size of the memory matrix, a plurality of lines is therefore required from the matrix cells to the matrix periphery. The size of a realizable matrix is limited as a result thereof.
U.S. Pat. No. 4,935,897 discloses a memory unit for use in a printer. The memory unit can be employed as a buffer memory for image data. A picture element can thereby be stored at each matrix point of the memory unit. Picture elements can be read out by designational control with a row decoder and a column decoder such that an image rotation thus ensues.
U.S. Pat. No. 4,875,190 discloses a two-dimensional memory unit that contains memory modules arranged in a matrix form. Each memory module itself is a two-dimensional memory capable of random access and organized in a matrix form. All memory modules are identical and are addressed with an address bus that is nine bits wide, as a result whereof a specific matrix cell that is the same in all memory modules can always be simultaneously selected.